The present invention relates to an electronic watch powered by an electric power source and including hands indicating the time rotating above a dial, a device displaying at least the date, this device being formed of first and second indicators on which are marked figures respectively indicating the tens and the units of said date, the date appearing through a large aperture made in the dial, and a control member able to be activated manually to allow the hands to be set to the correct time and the date to be set.
In most cases watches displaying the date are provided with a single disc or ring at the periphery of which figures from 0 to 31 are marked these figures appearing through an aperture made in the watch dial. By their very nature, date indications are thus of small dimensions and relatively difficult to read. In order to improve this situation and propose a date of large dimensions which is easy to read, there are available on the market watches provided with a so-called large date aperture through which appear a first indicator on which the figures of the tens of the date are marked and a second indicator on which the figures of the units of said date are marked.
The document CH 688,671 discloses such a large date aperture. In this document, the date display mechanism includes a tens indicator disc with four positions and a units indicator disc with ten positions. The mechanism includes a drive wheel completing one revolution per month and including two distinct irregular toothings. The first toothing includes thirty teeth for incrementing the tens indicator disc. The teeth of the first toothing are spaced by one 31st of a revolution so that one tooth is missing to form a complete circular toothing and that the incrementation of the units disc misses thus one step out of thirty one. The drive wheel is positioned angularly such that the 1 is the figure whose display is kept longest, the teeth of the second toothing being disposed such that the tens indicator disc is incremented, on the one hand, each time that the units indicator disc passes from 9 to 0 and, on the other hand, at the moment when the missing tooth would have activated the units indicator if it existed.
The complexity involved in mechanically driving the two date indicators from a drive wheel is evident from the foregoing description, and the complexity of the mechanism for setting the date described will not be described here.
When one has an electronic watch as is the case of the present invention, the above encountered difficulties are avoided by implementing the essential peculiarities of the present invention which consist in driving each of the first and second indicators forming the date by an independent motor.
By taking advantage of the presence of the aforementioned motors, the present invention also proposes displaying, by means of the same first and second indicators, the number of the month and the two last figures of the year, the date thus being able to be a perpetual calendar.